Multilayer photoimageable thick-films in microwave frequencies

Photoimageable thick film technology is by its nature compatible with the fabrication of multilayer structures. When in a single layer configuration of a microwave circuit very narrow coupling gaps are required which are difficult to obtain even by the most sophisticated photoimaging techniques, the solution is a double-layer structure where strong capacitive coupling can be accomplished by overlapping the conductor strips deposited on two conductor layers separated by a dielectric sheet. The paper presents the process of design and fabrication of single and double layer hairpin filters of centre frequency 12 GHz by photoimageable thick-film technology. Measured transmission and reflection characteristics are compared to simulated ones.